I read an article on how the ancient Egyptians were 90% vegetarian, but the research was based on the examination of mummies. This is very recent research (which, according to the subreddit's rules, I'm not allowed to ask a question about) but the article also stated that it had long been suspected that their diet was mostly plant-based. Does anyone here know what these earlier suspicions were based on? Because, since the poor were never mummified, research on mummies can only give us evidence on the diet of rich ancient Egyptians. What are some other ways to learn about the diet of a people that lived so long ago?
Some priests in the upper class may have been vegetarian, although most large temples seem to have kept cattle of some sort on their land. However, the question is a difficult one to answer simply because it's so broad. You're talking about a period between 3,100 BC and 600 AD spanning hundreds of cultural shifts and changes, not to mention a few conquests.
However, to give a broad answer, if anybody ate meat in Egypt regularly, it was the upper class. This can partly be inferred from various paintings, we see lots of nobles hunting and fishing, as well as tomb offerings. I believe there's actually a specific spell in the Book of the Dead to provide the deceased person with meat in the afterlife.
However, the poorer folk would have mostly had vegetarian fare, possibly with a bit of fish now and then. Egypt was a highly agrarian economy through most of its history, so they generally had plenty of grain, onions, lettuce and chickpeas to go around. There were exceptions to this though. On some festival occasions we have records of the king providing meat to his laborers.
Certain elite servants, such as royal messengers, are on record as having received fairly lavish rations. We get this information from various stele, wall carvings and preserved papyri. The Egyptians were very good about keeping records most of the time, and we have little reason to doubt the pharaohs exaggerated too much when recording the diets of their workers.
In short, the people of Egypt weren't so much 'vegetarian' as 'opportunistic.'
This is very recent research (which, according to the subreddit's rules, I'm not allowed to ask a question about)
Just FYI, recent research is not against the subreddit's rules. Research is being done all the time and it would be a very poor historian who ignored the most up-to-date research.
Events that have happened in the last 20 years are off-limits for discussion.